Ophthalmometer.



C. J. .TROPPMAN.

OPHTHALMOMBTBR. APPLICATION FILED MAY 22, 1911.V

Patented Dec. 3, 1912.

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STATES PATENT FIC.

CHARLES J'. TROPPMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO F. A. HARDY &COMPANY,

A CORPORATION OF ILLINOIS.

OPI-ITI-IALIVIOMETER.

To all 107mm it may concern: y

Be it known that I, CHARLES J. TROPP- MAN, a citizen of the UnitedStates, residing at Chicago, in the county of Cook and State ofIllinois, have invented a new and useful Improvement in Ophthalmometers,of which the following is a specification.

My invention has relation to ophthalmometers in which a telescope isdisposed with relation to luminous targets or mires so that the imagesof the targets or mires will be reflected into the telescope from thecorneal surface and refracting means such as a double or birefringentprism is employed to move longitudinally within the telescope so thatthe images as seen in the telescope may be moved together or separated.The location of the images as reflected from the cornea being dependentupon the curvature of the cornea, the location of the prism within thetelescope necessary to secure a certain relation of the images as seenfurnishes data from which the curvature can be ascertained. Theseconditions have already been utilized by disposing scales upon the meansfor moving the prism, the position of which indicates, either in radiior diopters, that is refractive power, the curvature of the cornealsurfacewhich will secure the desired relation of images at that positionof prism.

As the movement of the prism is not uniform for uniform changes ofcurvature or location of images, it has heretofore been necessary toprovide specially constructed scales, vand my invention consists inproviding the ophthalmometer with means which, for a given extent ofmovement will move the prism a progressively increasing or diminishingamount. Such a provision will permit of the employment of uniform scaleswhich are of advantage from both a manufacturing and operativestandpoint.

' My invention is illustrated in the accompanying drawing, in whichFigure 1 is a central longitudinal section of the telescope of anophthalmometer with my invention applied thereto; Fig. 2 is a transversesection o-n line 2 2 of Fig. 1, one scale wheel being shown inelevation; and Fig. 3 is a detail of the rack and eccentric gear.

Similar reference numerals refer to similar parts throughout the severalviews.

The reference numeral 1 designates the Specification of Letters Patent.

Application filed May 22, 1911.

rPatented Dec. 3,1912.

Serial No. 628,709.

telescopic tube in an ophthalmometer which is rotatably mounted in abearing, 2, and has provided upon its forward end a member, 3, (afragment of which is shown in Fig. 1) for holding the mires. The forwardend of the telescopic tube, 1, terminates in a nose piece 4, in which ismounted the objective lens or lens system, 5.

In the telescopic tube, 1, to the rear of the-bearing, 2, is alongitudinally disposed opening, 6, and mounted to move longitudinallywithin the telescope tube is a collar, 7 which carries a rack, 8,extending into the opening, 6.

A block, 9, is secured to the outer surface of the tube, 1, so as tocover the opening, 6, and in the block, 9, is a recess, 10, which opensupon each side.

In'the bottom of the recess, 10, is a rec tangular pocket, 12, andin thebottom of the pocketthe block is bored to form a cylindrical guide way13. Mounted to slide in the guide way is a pin, 14, upon the top ofwhich is a U-shaped yoke, 15, between the bottom of which and the bottomof the pocket 12, and about the pin, 14, is a coiled spring, 16, whichyieldingly holds the yoke, 15, in its most upwardly position.

In the tops of the arms of the yoke, 15, are provided bearings, 17, andmounted in the bearings, 17 ,is an arbor, 18, upon which and between thearms of the yoke is secured the eccentric gear, 19, which is heldyieldingly in mesh with the rack, 8, by the spring, 16, so that the gearand rack will not bind.

Suitably mounted within the collar, 7, is the double or birefringentprism, 20, and mounted upon the arbor, 18, are wheels 21 and 22, onwhich may be disposed scales for showing the radius of the cornealcurvature or the refractive value for the particular curvature which forthat position of the prism, 20, will secure the desired location of theimages in the telescope. In Fig. 2, a scale, 23, is shown upon theperiphery of the right hand wheel 22.

It will now be seen that by reason of the ecentric gear, 19, a movementof the periphery of the wheels, 21 and 22, through uniform distances orequal numbers of degrees of arc, will impart, through the arbor, 18 andeccentric gear, 19, an increasing or diminishing extent of movement tothe rack, 8, collar, 7, and prism, 20. By means of the selection of asuitable eccentricity of the gear, 19, a scale may be employed ofsuitable amplitude of divisional marks in which the markings are equaldistances from each other. Y

Having described my invention, l`what I claim as new and desire tosecure by Letters Patent, is

il. In an ophthalmometer comprising a telescope, mires disposed withrelation thereto so that images thereof will be reflected from thecorneal surface of' an eye into said telescope, movable refracting meansfor changing the kposition of said images as seen through said telescopeand means for moving said refracting means which will impart anincreasing or decreasing latitude of movement to said refracting meansfor equal movements of said moving means.

2. In an ophthalmometer, a telescope, mires fixed with relation to theoptical axis thereof, a double prism mounted within said telescope,r thebase whereof is transverse to said optical axis, an arbor, an eccentricconnecting said arbor with the mounting of said prism so as to' causesaid prism to move different distances for movements of said arborthrough equal arcs.

3. In an ophthalmometer, `a telescope, mires disposed so that-imagesthereof will be reflected from the eye under observation into saidtelescope, a double prism located transverse to the optical axis of saidtele scope in the path of the light from said mires, a rack carried bysaid prism, an eccentric gear meshing with said rack, an arbor extendingthrough said gear, and scales secured to said arbor.

4. In an ophthalmometer, a telescope,

mires disposed so that images thereof will be reflected from the eyeunder observation into said telescope, a double prism located transverseto the optical axis of said telescope in the path of the light from saidmires, a rack carried by said prism longitudinally of said optical axis,an eccentric gear meshing with said rack, an arbor extending throughsaid gear, and scales secured to said arbor.

5. In an ophthalmometena telescope, mires disposed so that imagesthereof will be reflected from the eye under observation into saidtelescope, a double prism located transverse to the optical axis of saidtelescope in the path of the light from said vmires, a rack carried bysaid prism, an eccentric'gear, means for holding said gear yieldingly inmesh with said rack, an arbor extending through said gear, and scalessecured to said arbor.

6. In an ophthalmometer comprising a telescope for viewing the eye,mires disposed so that images thereof will be reflected from the eyeunder observation into said telescope, a movable refractor transverse tothe optical axis of said telescope, a uniform scale, and meansconnecting said scale, and said refractor,'whereby movements of saidscale through equal extents will impart increasing or diminishingamplitudes of movement to said refractor.

In testimony whereof I have hereunto set my hand in the presence of twowitnesses.

CHARLES J. TROPPMAN.

. Witnesses:

JOHN H. HARDIN, BENJ. T. RooDHoUsn.

Copes'of this patent may be obtained for five cents each, by addressingthe Commissioner 'of Patents, washington, D. c.

